1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method used for forming a film such as an interlayer insulating film on a substrate such as a semiconductor wafer.
2. Description of the Related Art
In the manufacturing process of a semiconductor device, known as a method of forming a dielectric film such as an interlayer insulating film on a semiconductor wafer is a method of coating a wafer with a coating liquid by using an SOD (spin on dielectric) system so as to form a coated film, followed by applying a physical treatment such as a heat treatment to the coated film. In general, a spin coating method, in which a coating liquid is supplied onto substantially the center of a semiconductor wafer that is stopped or rotated, followed by rotating the semiconductor wafer at a prescribed rotating speed so as to expand the coating liquid onto the entire surface of the semiconductor wafer, is used as a method of forming a coated film.
Recently, a material having a low dielectric constant is required for forming an interlayer insulating film and, thus, various materials, which are so-called “low-k” materials, are being developed. Some of these low-k materials are required to be processed with an ammonia (NH3) gas containing a prescribed amount of a water vapor.
FIG. 1 is a cross sectional view showing a conventional aging unit 90, which is used as a process unit for processing a wafer under an ammonia gas containing a water vapor. As shown in FIG. 1, the aging unit 90 comprises a disposing plate 91 on which a wafer W is disposed and a chamber 92 housing the disposing plate 91 consisting of a lower container 92a and a lid 92b. A gas supply port 95a for supplying an ammonia gas containing a water vapor (NH3/H2O) into the chamber 92 is formed in the bottom portion of the lower container 92a. On the other hand, an exhaust port 95b for exhausting the ammonia gas containing a water vapor and introduced into the chamber 92 is formed in the central portion of the lid 92b. 
A bubbler, in which an ammonia gas is blown into an ammonia water stored in a tank for bubbling the ammonia water, is used in general as an apparatus for supplying an ammonia gas containing a water vapor into the aging unit 90. The ammonia water within the bubbler is maintained at a constant temperature.
However, the temperature of the disposing plate 91 is not controlled in the conventional aging unit 90. Therefore, the processing temperature of the wafer W within the aging unit 90 is greatly affected by the environment of the installing site of the aging unit 90. In this case, it is necessary to change the processing time in the aging unit 90 in order to maintain constant the degree of progress in the reaction of the coated film. For example, it is necessary to conduct the operation to determine the conditions for determining the processing time in accordance with the processing environment at a frequency of once a day. It is also necessary to change the tact time by changing the determined processing time. Further, if the processing time in the aging unit 90, which is obtained by the operation to determine the conditions, is long, e.g., 5 minutes, a problem is generated that the through-put of the wafer processing in the SOD system is lowered.